I bought this game on steam. At first i had no idea what's going on, then I clicked the manual button in steam and I found the manual. It's not needed, but it's a fun and effective way to keep track of your spells and get some extra story. Armed with the manual and a digital pen I started playing this game and I must say it is one of the most enchanting games I've ever played.
(The one sold on steam is the talkie version, the voice acting is top notch for a 1990 games, so definitely check it out)
EDIT: Actually i found out that it isn't the manual itself but rather the Book of Patterns. I'm really glad lucasarts uploaded this as the manual and not the actual manual.